1. FIELD OF THE INVENTION:
This invention relates to an improved tool for effecting the washing of sand or particulates from casing perforations and channels in formations in subterranean wells.
2. HISTORY OF THE PRIOR ART:
Most producing subterranean oil wells are plagued with sand accumulating in the channels or flow passages in the producing formation and the casing perforations through which the production fluid must flow. It has been the common practice to reduce the accumulation of such sand by establishing a reverse flow of a washing fluid through the casing perforations and into the channels of the production formation, and then retrieving the sand laden washing fluid from the well. The removed sand is then replaced by gravel.
Washing tools heretofore employed conducted the washing fluid downwardly to the vicinity of the production formation through a tubing string, disposed within the casing, to a tubular body wash tool having sealing engagement with the casing wall both above and below the casing perforations. A relatively high pressure, high volume fluid was then introduced through the central tubing string and permitted to discharge through the casing perforations and into the channels of the production formation, carrying with it any sand disposed in its path. Sand laden fluid then flowed downwardly through the apertures normally existing between the exterior of the casing wall and the well bore and entered the bottom of the casing to flow upwardly. A crossover passage was provided in the bottom end of the wash tool to direct the sand laden, upwardly flowing fluid around the portion of the wash tool supplying the washing fluid and thence into the casing annulus for removal from the well.
This particular arrangement was obviously complicated and expensive in requiring a crossover configuration to be incorporated in the wash tool. More importantly, the upward flow path for the sand laden washing fluid was of sufficiently large area that it was difficult to maintain sufficient upward fluid velocity to insure that all of the loosened sand would be carried to the surface, particularly in deviated wells.